grand prix gt 2001 trany problems

can anyone help me to diagnostic what's the problem with my trany,
my transmission is shifthing a little bit hard!
and only start doing this after driving for awhile,and if i stop for a few minutes and restart driving again it shift's smooth again for a few miles and go back to shifthing hard.
can this be a sensor or vacumm,or is the sign of the tranny goine bad?
thanks in advance for your help,

p.s. there is no engine light on !

Hello!

Has the tranny been serviced recently? If not, you might want to replace the fluid and filter in it.

Another posible cause would be a dirty MAF sensor; the PCM relies on it and other sensors to provide better performance. Remove it with a Tamper proof torx bit (I can't recall the actual number) and use some MAF cleaner or, ir not available, electric contact cleaner both available at most autoparts stores.

Oscar.

There are some tranny codes that DON'T TURN ON THE CE LIGHT....

If a code sets, the PCM may command full line pressure, causing hard shifts.....

When you shut the car off, everything resets....probably shifts fine....then the code sets, and the PCM commands full line pressure again.....

Places like AutoZone will read codes for free....

If a code sets, the PCM may command full line pressure, causing hard shifts.....

Places like AutoZone will read codes for free....

Which could also be the case of the MAF, that's why I suggested to take a look and clean it first.

Autozone will read the codes, but the scanner they use will only read some BASIC transmission codes if they are set. The use of a fully capable scanner would be a better idea but I don't know how much would a shop charge. In other words, the fact that the autozone scanner doesn't shows any codes still doesn't means there are no codes at all...

Oscar.

"Autozone will read the codes, but the scanner they use will only read some BASIC transmission codes if they are set."

What the heck are you talking about? Read only "basic" codes? If a code is set, it will be read by the scan tool......

Of course but that doesn't means a low end scanner like most used at autoparts stores will read every single code, as well it won't perform the diagnostic tests a high end scanner can. Hence the need of a proper diagnostic.

The fact that the CEL is not on doesn't means there are no codes, just like you said; just like the fact that a scanner is not showing any codes doesn't means there are no problems...

If it makes you feel happier I'll say generic codes instead of basic codes.

I am not sending him to AutoZone for a diagnostic test, just to read codes....I'm sure their scanner is more than capable of reading gereric as well, as dealer specific, for example, like a P1811....